One of the zones of deep earthquake hypocentres whose existence was first demonstrated in 1927 by the Japanese seismologist Kiyoo Wadati. The zones were mapped in the 1940s and 50s by Hugo Benioff. They dip from near-surface to a maximum depth of approximately 700 km and are associated with oceanic trenches, island arcs, volcanic chains, and young fold mountains, and are thought to indicate active subduction. See subduction zone.